Beloved archetype .
The phrase itself comes out of the smart, self-depracating mouth of Amy Archer, i.e. Jennifer Jason Leigh's character in The Hudsucker Proxy.
You know...for kids.
These girls dress and talk smart, and hold fun girl jobs like reporting and secretarial work. They know what's up.
Greatly more so than the dumb boys over whom they tend to swoon.
See also: His Girl Friday. Which, if memory serves, starred Rosalind Russell.